The present invention concerns an assembly for the transport and storage of radioactive fuel elements.
For the conveyance of fuel elements it is known to use sealably closed transportation flasks. During conveyance irradiated fuel elements are submerged in liquid (for example water) within the flask to dissipate heat generated by the decay of fission products and thereby limit the fuel temperature. While provision must be made for change of volume of the liquid in the flask, it is important that irradiated fuel elements are submerged at all times during conveyance.
In British Pat. Specification No. 1378681 there is described and claimed a sealably closable fuel element transportation canister for containing fuel elements submerged in liquid having self-regulating ullage means arranged so that within a chamber for containing the fuel elements the free space can be maintained full of liquid. In particular there is described a canister having a primary chamber for containing the fuel elements submerged in liquid, a secondary chamber for containing liquid and pressurised gas and a duct interconnecting the chambers and arranged for forming an air lock there between whereby the free space in the primary chamber can be maintained full of liquid.
It is now considered that it is not necessary for the chamber containing the fuel elements to be full of liquid although there must be sufficient liquid in the chamber for the fuel elements always to be submerged in the liquid. This condition is important for transportation flasks in which the fuel elements are loaded into the flask in one orientation and the flask is transported in a second orientation.